1. Technical Field of the Invention
The present invention relates to an injection apparatus and, more particularly, to an sample injection apparatus for use in a liquid chromatograph that can perform preparative liquid chromatography with high efficiency.
2. Description of the Prior Art
In a liquid chromatograph using a liquid solvent (elution solvent) as a mobile phase, it is required that a sample liquid and a solvent be delivered in sequence into a column packed with a stationary phase, and an apparatus, which is called an injector, is generally used with the liquid chromatograph. However, injectors commonly used in the analytical liquid chromatographs are not suitable for a large quantity of sample injection required in a preparative liquid chromatography. Therefore, a sample liquid has to be injected directly into the column by opening the upper end of the column, which is very troublesome work.
An injector intended for easing such a troublesome work is known from the applicant""s Japanese Utility Model Publication No. Hei 1(1989)-41473. The known injector has a cylinder including therein three plugs of a fixed plug, a floating plug, and a movable plug which are vertically arranged in order and having a ring-shaped recess in an inside wall thereof. According to this injector, as the floating plug rises, the sample liquid above the floating plug is delivered, while, when the floating plug is moved up to the recess, the solvent below the floating plug is delivered passing through clearances therebetween. This can provide the advantage that a large quantity of the sample liquid and the solvent can be delivered in sequence into the column without any troublesome work and with speed by use of only a single injector.
However, even in the use of the injector disclosed in the publication above, delivery of several kinds of sample liquids into the column for separation requires that a plurality of injectors packed with the sample liquid be each replaced in sequence with the next injector after each completion of the delivery of the sample liquid in each of the injectors. These works are of troublesome and it takes long time for the replacement. Thus, the prior art has a disadvantage that preparative chromatography of sample liquids cannot be done efficiently.
Accordingly, it is a primary object of the present invention to provide an injection apparatus for permitting preparative chromatography of the sample liquids packed in a plurality of injectors to be efficiently done.
An injection apparatus according to the present invention comprises a first switching valve which is selectively connected to any of a plurality of injectors at one end sides thereof; a second switching valve which is selectively connected to any of the plurality of injectors at the other end sides thereof; a third switching valve which is connected to the second switching valve and is selectively connected to any of a plurality of columns at one end sides thereof; and a fourth switching valve which is selectively connected to any of the plurality of columns at the other end sides thereof.
According to the injection apparatus of the present invention, since any of the plurality of injectors can be selectively connected between the first switching valve and the second switching valve, the switching of these two valves can permit any one of the plurality of injectors to be connected to the upstream side and the third switching valve. Also, since any of the plurality of columns can be selectively connected between the third switching valve and the fourth switching valve, the switching of these two valves can permit any one of the plurality of columns to be connected to the second switching valve and the downstream side. Accordingly, the sample liquids in the plurality of injectors can be delivered in sequence into any selected columns by the selective switching among the first to fourth switching valves.
Then, an automatic switching operation of the 1st to 4th switching valves will be permitted once the injectors and the columns are installed in the injection apparatus. This can provide a relatively simple work and also can save time for the replacement of the injectors and the columns. Thus, an efficient analysis and dispense can be achieved in a short time.
It should be noted that upon using the injection apparatus of the present invention, one injector and one column are not necessarily required to be associated with each other. In other words, it is not necessary to change the column every time the injector is replaced. One column may be brought into association with two or more injectors.
The injector known from the aforementioned JP Utility Model Publication No. Hei 1(1989)-41473 may be used as the injector in the present invention. In the present invention, two or more injectors are of sufficient, but actually, 5 to 15 injectors are of optimal in terms of readiness in handling and economics.
Preferably, the rotary valve disclosed by the applicant""s JP Patent Laid-Open No. Hei 11(1999)-201955 is used as the switching valve. The rotary valve comprises a stator and a rotor which are allowed to rotate in contact with each other. The stator has one central through hole at the center thereof and a plurality of through holes on the circumference of a circle in the peripheral part thereof. The rotor has one aperture at the center thereof and one aperture in the peripheral part thereof. The both apertures are communicated with each other in the interior of the rotor or thereunder. The use of this rotary valve is of advantageous in that the fluidal contact area in the contact surface of the rotor and the stator can be reduced, as compared with the use of a general type of switching valve, and as such can retard occurrence of contamination.
It is preferable that in the injection apparatus of the present invention, at least one liquid sensor is provided between the second switching valve and the third switching valve. In this case, only when liquid is detected by one liquid sensor, the switching of the second switching valve and the third switching valve can be permitted to deliver the liquid in the injector to the associated column. This can permit the entry of almost no air into the columns, so the sample liquid can be separated adequately in the column. The use of only the single liquid sensor will have the difficulty in discharging out the air completely from the column in such cases that the liquid is delivered catching the air therein. Accordingly, two or more liquid sensors are of preferable.